JP3119976B2 - Flange back mechanism for single-lens reflex camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-lens reflex camera with interchangeable photographic lenses, and more particularly, to a flange-back mechanism of a single-lens reflex camera for adjusting a focus by adjusting a back focus.

[0002]

2. Description of the Related Art In a general single-lens reflex camera, focus adjustment for each distance to a subject is performed by a distance ring of a lens. The one that automatically drives this by an in-body motor or an in-lens motor has been put into practical use as an AF single-lens reflex camera. In each case, a dedicated AF lens is used, and it has been impossible to convert a conventional MF lens into AF. In addition, the conventional single-lens reflex camera employs a fixed flange back mechanism, and for example, it was impossible to take an image closer than the shortest shooting distance inherent to the lens.

To solve this problem, one of the inventors of the present invention is to provide a camera body mainly with a driving power source, a driving mechanism, a camera holding grip having a release button, and the like based on a lens mount in which a conventional lens can be mounted and replaced. A single-lens reflex camera that consists of a fixed front part of the main body and a movable rear part mainly including a distance measuring mechanism including a distance measuring element, a film exposure mechanism, and a finder, and adjusts the focus by the amount of movement of the rear movable side. (Japanese Patent Application No. Hei 4-226556)
etc). According to this, the shortest photographing distance of the conventional lens can be further reduced, and AF is realized by automation.

In this case, the position of the reference flange back common to the various lenses mounted on the camera is very important, and this position is the reference position for focus adjustment as an infinity photographing position. For this reason, it was in a fixed stop position like the conventional camera. This is because manual shooting is required for a conventional MF camera, and in shooting in that mode, an infinite reference position must be accurate in order for the distance scale of the lens distance ring to be accurate. It is.

[0005]

However, on the other hand, in order to convert the camera into AF and perform AF shooting as described above, it is necessary to set the distance ring at an infinity position when mounting the shooting lens. Condition. The conventional lens does not have a lock mechanism like an AF-only lens, so it can be moved arbitrarily, and when actually used, it is not always set at the infinite position, or it is slightly shifted even if the photographer intends to set it In the state, the response of AF was impossible. That is, if the distance ring of the lens is slightly deviated from the infinity position, AF photography up to infinity is impossible. Therefore, the photographer always has to pay attention to the position of the distance ring of the lens, which is troublesome.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem, and has a structure in which the lens can be further moved shorter than a reference flange back position of the lens.
An object of the present invention is to provide a flange back mechanism of a single-lens reflex camera in which a movable range is extended to a super infinite position of a lens to be mounted. Another object of the present invention is to provide a movable position detecting means for detecting the position of the opening of the rear block with respect to the mount surface on which the lens is mounted, thereby enabling precise displacement measurement, and allowing the position of the rear block to be moved arbitrarily to be determined in advance. It is another object of the present invention to provide a single-lens reflex camera flange-back mechanism capable of precisely controlling a reference flange-back position, a super-infinite position, and a close-response movable limit position.

[0007]

In order to achieve the above object, a flange back mechanism of a single-lens reflex camera according to the present invention comprises a flange surface of a mount for mounting and connecting an interchangeable photographing lens group and a camera body and the lens group. And a mechanism capable of adjusting the focal length by adjusting the flange back of the camera body in addition to the distance adjusting ring of the lens group. Then, the position of the reference flange back of the mounting lens group in the movable range of the optical axis parallel to the flange surface of the mount in the front block of the camera body and the film opening in the rear block is the focal point of infinity shooting, A back focus adjustment single-lens reflex camera configured to increase the distance of a flange back according to finite distance shooting from a position. Te, the movable range of the film opening of the camera body and movable in the up shorter ultra infinite position than the size of the reference flange back is mounted
Infinity shooting with the reference flange back position of the shooting lens group
Focusing at infinity is possible even if it is out of the shadow position
It is composed .

According to the present invention, in the above configuration, the camera
Flange surface of lens mount on front block of main unit and front
Adjust the distance between the camera body and the rear block opening.
It is configured to be performed by AF control means. According to another aspect of the present invention, in addition to the above-mentioned configuration, the present invention further provides a movable position detecting means for detecting a position of an opening of the camera body rear block with respect to a flange surface of a lens mount of the camera body front block. And control means for setting the dimension of the reference flange back based on the position detection data of the movable position detection means. Further
The camera body front block according to the present invention includes an AF
Camera holding group having drive mechanism and release button
A lip, wherein the rear block of the camera body is
Structure, finder mechanism, exposure mechanism and film feeding mechanism
It is provided with.

[0009]

According to the above arrangement, since the flange back inherent to the lens is further reduced, that is, it can be moved to a super infinity, it is set at an infinite position of the distance ring position of the photographing lens which is a condition for AF photographing. Operation becomes easy. In other words, the AF response can be performed from the closest to infinity only by placing the taking lens near infinity. For this reason, while carrying the camera, the trouble that the distance ring of the lens is shifted and the AF does not fully operate and the infinite position are not shifted are eliminated.
The anxiety of the photographer is resolved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. First, the principle of the present invention will be described in detail with reference to FIGS. FIG. 1 is a sectional view of a general camera for explaining a flange back. The distance between the reference position and the imaging position where the lens mount surface 20a common to the interchangeable lens group 20 and the lens mount surface 21a on the camera body side are in contact is the flange back L, and the distance ring of each interchangeable lens Is infinite, the position where the subject image at infinity is formed has a value determined for each manufacturer. For example, it is standardized as L = 45.5 mm, and all interchangeable lenses are common.

FIG. 2 shows a lens group of the interchangeable lens shown in FIG.
FIG. 4 is a cross-sectional view of a camera in which the number of equivalent lenses has been replaced, showing that the focal length f of the lens is on an image forming surface. FIG. 3 is a cross-sectional view of the camera for explaining equations for calculating the focal length and the photographing distance. It is known that when the focal length is f, the distance between the principal planes of the lens is δ, the extension amount is Bf, and the shooting distance is Rx, the focal length f and the shooting distance Rx are calculated by the following equations. f ² = x Bf (x) (1) Rx = 2f + δ + x + Bf (x) (2) According to the above equation, the distance ring of the taking lens is set to infinity as shown in FIG. It can be seen that a finite distance focusing can be achieved by adjusting the mounting surface distance Bf of the camera body. That is, it can be seen that the flange back should be made variable by adding the adjustable distance Bf to the reference flange back L.

FIG. 4 is a sectional view of a camera for explaining the principle of making the flange back variable in the present invention. Reference the shortest distance of the flange back L
It is configured to be a super infinite position by a small distance ρ, which is shorter than that. By setting the variable payout distance s to (Bf + ρ) as shown in FIG. 5, the infinity position of the distance ring of the lens to be attached is shifted, and even if the distance is pulled out by ρ, infinity shooting is possible by flange back adjustment. , And the object can be achieved.

FIG. 6 is a schematic sectional view of a camera for explaining an embodiment of the flange back mechanism of the single-lens reflex camera according to the present invention. The camera body front block A includes an interchangeable lens 9, a lens mount 1, an AF driving mechanism 7, and a grip having a release button (the release button and the grip are not shown).
The rear block B of the camera body is an up-down mirror 13,
It includes a finder mechanism 5, an aperture 10, an exposure mechanism, a film feeding mechanism, and a distance measuring mechanism 3. Light from a subject (not shown) passes through the interchangeable lens 9, the optical path is bent upward by 90 degrees by the up-down mirror 13, enters the finder mechanism 5, and becomes parallel to the main optical axis by the pentaprism 5 a. It is bent and reaches the eyepiece 5b. Part of the subject light that has passed through the interchangeable lens 9 also enters the AF mirror 3a of the distance measuring mechanism 3, the optical path is bent downward, and reaches the AF sensor 3c via the AF lens 3b.

The AF drive mechanism 7 includes a flange back drive motor 7a, an encoder 6 for detecting the rotation speed of the motor 7a,
Gears 7b, 7c, lead screw 7d and female screw 7
e. Flange back drive motor 7a
Is transmitted to the lead screw 7d through the gears 7b and 7c at a reduced speed. The lead screw 7d is screwed into a female screw 7e provided at the base of the rear block B of the camera body, and the rotation of the lead screw 7d changes the distance in the optical axis direction between the front block A and the rear block B of the camera body. I do. Thus, the distance between the lens mount 1 and the aperture (opening) 10, that is, the flange back can be adjusted. The distance between the front block A and the rear block B of the camera body can be changed by s, that is, by an amount of (Bf + ρ). At the reference position (the distance L between the front block A and the rear block B of the camera body) at which the focal point of the lens is at the infinity position (a state in which the distance ring is adjusted to the infinity position), ρ is further reduced in the direction of shortening. The distance can be changed by Bf in the increasing direction.

Information indicating the positional relationship between the front block A and the rear block B of the camera body can be detected by a position detection switch 8 which is a movable position detection means. The code pattern substrate 8a constituting the position detection switch 8 is fixed to the base of the front block A of the camera body, and its contact 8b
Are fixed to the base of the camera body rear block B, respectively. When the distance between the front and rear blocks A and B changes, the code pattern changes accordingly, and a flange back (hereinafter referred to as “FB”) position detection signal can be obtained. In addition, other methods such as sliding resistance may be used as the position detection switch 8 in addition to the code pattern. A member connecting the front block A and the rear block B of the camera body is provided with a rail on the front block A and a roller on the rear block (both rails and rollers are not shown). By configuring to roll, the distance between the two blocks can be changed smoothly so that a load is not applied as much as possible. Note that a linearly moving bearing or the like may be used as the other connecting member.

A guide rod (not shown) is provided on the front block A of the camera body opposite to the lead screw 7d with the up-down mirror 13 interposed therebetween. A guide hole (not shown) is provided in the rear block B of the camera body as a member for guiding this. The guide rod slides in the guide hole with the rotation of the lead screw 7d.
The camera body rear block B is guided to the camera body front block A in cooperation with d. Thereby, the optical axis can be moved so that the optical axis between the two blocks does not shift, and the aperture surface and the lens mount surface are kept parallel. A bellows 4 is provided between both ends of the block where a gap is generated due to a change in the positional relationship to prevent light leakage.

FIG. 7 is a circuit block diagram showing an embodiment of the control circuit section in the present invention. Code pattern board 8a
Outputs an FB position detection signal, an encoder 6 outputs an encoder signal, and an AF sensor 3c outputs a ranging signal (AF information). The AF control circuit 17 inputs the FB position detection signal, the encoder signal, and the distance measurement signal, and drives the FB drive motor drive circuit 15 based on an instruction signal from the AF / MF switch 16 and an ON / OFF signal of a power switch (not shown). Then, the AF control mechanism 7 is controlled.

FIG. 8 is an operation diagram of the camera according to the present invention.
6 is a flowchart for explaining an operation accompanying switching of an AF / MF switch. AF / MF switch 1
When 6 is switched to MF, a reference flange back return command is sent to the AF control circuit 17 (S801).
The AF control circuit 17 can know the distance between the front block A and the rear block based on the FB position detection signal from the code pattern 8a. The AF control circuit 17 determines whether or not the current position of the BF is at the reference position L (S802). If it is at the reference position L, the setting of the MF shooting mode is completed (S808). If it is not the reference position L, it is next determined whether or not it is on the forward (super infinite) side of the reference position (S803).

If it is shifted rearward, it is calculated how much to move forward to the reference position (S804).
By controlling the B drive motor drive circuit 15, the motor 7 is driven to move the rear block B to the reference position (S80).
5). On the other hand, if it is shifted to the front side, it is calculated how much to move to the reference position backward (S806).
By controlling the B drive motor drive circuit 15, the motor 7 is driven to move the rear block B to the reference position (S80).
7). Therefore, when focusing by manual adjustment of the distance ring of the lens, the flange back is automatically set to the reference position L. When the AF / MF switch 16 is in the AF mode, the camera enters a standby state.

In the above embodiment, a grip portion is provided on the front block A of the camera body, and the block A is used as a reference.
Although the case where the flange back is adjusted by moving the rear block B has been described, the grip portion is provided on the rear block B, and the front block A is
It is apparent that the same operation is performed even if is movable. In addition, an AF driving mechanism may be provided in the rear block B accordingly. Furthermore, if the film surface, the AF sensor surface, and the finder surface can be configured to be linked in an optically conjugate positional relationship, it is not always necessary to mount the AF distance measuring mechanism, the finder mechanism, and the like on the rear block.

[0021]

As described above, according to the present invention, in the single-lens reflex camera of the back focus control type, the flange back of the camera when the distance ring of the interchangeable lens is set at infinity is shorter than the dimension of the reference position. It is configured so that The reference position of the flange back of the already proposed back focus control type single-lens reflex camera is set by mechanically applying it to the minimum distance, so that the distance ring of the interchangeable lens is infinite If the camera is deviated from the distant position, there is a problem that it is impossible to perform shooting at an infinite position by AF control, and the photographer must always pay attention to the position of the distance ring.

However, according to the present invention, even if the distance ring is slightly shifted from the position at infinity, the distance ring can be moved in the shortening direction. There is an advantage that shooting at infinity can be performed and anxiety of the photographer during shooting can be eliminated. In addition, when focusing is performed by the MF operation, the configuration is such that the flange back is automatically brought to the dimension of the reference position, so that there is no problem in the manual focusing operation. .

[Brief description of the drawings]

FIG. 1 is a sectional view of a general camera for explaining a flange back.

FIG. 2 is a sectional view of a camera in which a lens group of the interchangeable lens of FIG. 1 is replaced with one equivalent lens.

FIG. 3 is a cross-sectional view of a camera for explaining equations for calculating a focal length and a shooting distance.

FIG. 4 is a sectional view of a camera for explaining the principle of variable flange back in the present invention.

FIG. 5 is a sectional view of a camera for explaining a variable payout distance based on the principle of the present invention.

FIG. 6 is a schematic sectional view of a camera for explaining an embodiment of a flange back mechanism of the single-lens reflex camera according to the present invention.

FIG. 7 is a circuit block diagram illustrating an embodiment of a control circuit unit in FIG. 6;

FIG. 8 is a flowchart for explaining the operation of the control circuit unit in FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Lens mount 2 ... Film surface 3 ... Distance measuring mechanism 4 ... Bellows 5 ... Finder mechanism 6 ... Encoder 7 ... AF drive mechanism 8 ... Position detection switch 9 ... Interchangeable lens 10 ... Aperture 11 ... Press plate 13 ... Up-down mirror 15 ... Motor drive circuit 16 AF / MF switch 17 AF control circuit

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI G03B 13/36 G03B 3/00 A 17/14 (72) Inventor Nobuo Kitamura 2-14-9 Tamagawadai, Setagaya-ku, Tokyo Kyocera Inside the Tokyo Yoga Office (72) Inventor Tadaaki Ishikawa 2-149-9 Tamagawadai, Setagaya-ku, Tokyo Kyocera Corporation Inside the Tokyo Yoga Office (72) Inventor Shin Yasuhara 2- 14-9 Tamagawadai, Setagaya-ku, Tokyo No. Kyocera Corporation Tokyo Yoga Office (56) References JP-A-2-24640 (JP, A) JP-A-5-173225 (JP, A) JP-A-5-203864 (JP, A) −4470 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03B 17/02 G02B ⁷ /02-7/10 G03B 3/04 G03B 17/14

Claims (4)

(57) [Claims] 1. A structure in which a distance between a flange surface of a mount for mounting and connecting an interchangeable photographing lens group and a camera body and a film photosensitive surface which is an image forming focal plane of the lens group is adjustable. In addition to the distance adjustment ring of the lens group, the camera body has a mechanism that can adjust the focus by adjusting the flange back of the camera body, and the film opening on the flange surface of the mount on the front block of the camera body and the rear block. A back focus adjustment single lens configured to set the position of the reference flange back of the mounted lens group as the focal point for infinity shooting in the movable range parallel to the optical axis, and to increase the distance of the flange back from the position according to finite distance shooting. A reflex camera, wherein the movable range of the film opening of the camera body is further shorter than the dimension of the reference flange back. And movable in the up ultra infinity position, the reference flag of the photographing lens group to be attached
When the position of the image back is out of the shooting position at infinity
However, a flange-back mechanism for a single-lens reflex camera, characterized in that focusing at infinity is possible . 2. The single-lens camera according to claim 1, wherein the distance between the flange surface of the lens mount of the front block of the camera body and the opening of the rear block of the camera body is adjusted by AF control means. Flange back mechanism for reflex cameras. 3. A movable position detecting means for detecting a position of an opening of the rear block of the camera body with respect to a flange surface of a lens mount of the front block of the camera body, and a reference flange based on position detection data of the movable position detecting means. 3. A flange back mechanism for a single-lens reflex camera according to claim 1, further comprising: control means for setting a size of the back. 4. The camera body front block includes a camera holding grip having an AF driving mechanism and a release button, and the camera body rear block includes a distance measuring mechanism, a finder mechanism, an exposure mechanism, and a film feeding mechanism. 4. A flange back mechanism for a single-lens reflex camera according to claim 1, wherein: